Not applicable.
Not Applicable.
This invention relates to wheel balancers and in particular to improved drive systems, safety circuitry, and displays working in conjunction with said drive systems for wheel balancers.
The determination of unbalance in vehicle wheels is carried out by an analysis with reference to phase and amplitude of the mechanical vibrations caused by rotating unbalanced masses in the wheel. The mechanical vibrations are measured as motions, forces, or pressures by means of transducers, which convert the mechanical vibrations to electrical signals. Each signal is the combination of fundamental oscillations caused by imbalance and noise.
It is believed that the drive systems for currently available balancers could be improved to aid in operation.
Even when a wheel/tire assembly is balanced, non-uniformity in the construction of the tire as well as runout in the rim can cause significant vibration forces as the wheel rolls under vehicle load. Most tire manufacturers inspect their tires on tire uniformity machines and grind rubber off the tires as required to improve rolling characteristics of the tires. Even after this procedure, tires will often produce vibration forces (not related to imbalance) of 20 pounds as they roll on a smooth road. To put this in perspective of balancing, a 0.8 ounce balance weight is required to produce a 20 pound vibration force on a typical wheel traveling at 70 mph.
Many conventional balancers also assume that the wheel/tire assembly which is suitably balanced under an essentially no-load condition will also be suitably balanced when installed on the vehicle and subjected to the substantial load represented by the weight of the vehicle. This assumption is not valid under all conditions. It would be preferable in many circumstances to simulate loaded conditions to improve the results of the balancing operation.
Among the various objects and features of the present invention is a wheel balancer with improved performance.
Another object is the provision of such a wheel balancer which is capable of simulating loads on the wheel/tire assembly.
Other objects and features will be in part apparent and in part pointed out hereinafter.
In a first aspect of the present invention, a wheel balancer includes a shaft adapted for receiving a wheel/tire assembly, the shaft having a longitudinal axis and being rotatable about the axis so as to rotate the wheel/tire assembly removably mounted thereon, a motor operatively connected to the shaft for rotating the shaft about its longitudinal axis, thereby rotating the wheel/tire assembly, a load roller for applying a generally radial force to the wheel/tire assembly during rotation of the wheel/tire assembly so that loaded wheel/tire assembly measurements may be determined while the force is applied thereto and a control circuit responsive at least to the loaded wheel/tire assembly measurements and to a tire stiffness value to make a determination of a predetermined uniformity parameter.
In a second aspect of the present invention, a method is provided using a shaft adapted for receiving a wheel/tire assembly having a longitudinal axis and being rotatable about said axis so as to rotate a wheel/tire assembly removably mounted thereon, a motor operatively connected to the shaft for rotating said shaft about its longitudinal axis, thereby rotating the wheel/tire assembly, and a load roller for applying a generally radial force to the wheel/tire assembly during rotation of the wheel/tire assembly, the method including determining the loaded wheel/tire assembly measurements while the force is applied to the wheel/tire assembly, providing a tire stiffness value for the wheel/tire assembly and determining a predetermined uniformity parameter of the tire or wheel/tire assembly at least in part from the loaded wheel/tire assembly measurements and the tire stiffness value.